MARCH 12-13,
1993 DERECHO"The
'Storm of the Century' or 'Superstorm' Derecho"

Affected Florida, southeast Georgia, Cuba, and adjacent waters

On
Friday, March 12, 1993, a strong low pressure system formed in
the Gulf of Mexico. This low pressure system continued to strengthen
dramatically and moved northeast to the mid-Atlantic coastal
region by Saturday evening, March 13th. Besides producing a record
snowstorm over the eastern United States, this low pressure system
was accompanied by an intense squall line with embedded bow echoes
ahead of the system's cold front (Figures 1 and 2). The squall line produced a
serial derecho as it swept across the Florida peninsula, Cuba, and adjacent
waters. The squall line reached the northern part of Florida's west
coast and western Cuba between 11 p.m. and midnight (EST) on the
evening of the 12th. After causing much damage and producing many
casualties, the storm line moved off the southeastern coast of
Florida around 5 a.m. on the 13th, and departed central Cuba
after sunrise.

As
shown in Figure 1, much wind damage occurred across Florida,
with measured wind gusts reaching a maximum of 96 mph in the Tampa
Bay area. Supercells and small-scale bowing segments within the squall line (Figure 3) produced
tornadoes and/or tornado-like damage over the northern half of the Florida peninsula, with
some of the damage reaching F2 intensity.

Seven people were killed and 79 were injured from storm winds
and embedded tornadoes as the derecho-producing squall line raced through the state.
Storm winds blew down countless trees, power poles, and power lines, and tore roofs off homes.
Mobile homes were severely damaged, and trucks were overturned.

Figure
2. Thirty-eight-hour infrared data satellite loop showing development and progress of the
derecho-producing squall line associated with the "Storm of the Century" that affected
the eastern third of the United States on March 12-13, 1993. "Ping-pong" animation begins at 7:00 a.m.
EST (1200 UTC) Friday, March 12 and ends at 9:00 p.m. EST Saturday, March 13 (0200 UTC March 14). Color enhancement scale
not shown, but cloud tops colder than -55 &degC appear dark blue (approximately 14 km or 46,000 ft), and those colder than
-60 &degC, light blue (approximately 15 km or 50,000 ft). The squall line forms over the north central Gulf of Mexico
early in the loop and subsequently develops southward across the Yucatan peninsula and western Caribbean Sea, comprising
the southern end of the prominent "comma cloud" associated with the parent low pressure system. The intense low was centered
over southern Delaware at 9.00 p.m. March 13 and was responsible for an expansive area of heavy snow and/or high winds over
tbe eastern United States. At its greatest extent, the squall line reached from Central America to off
the coast of Georgia.

Figure
3. Seven-hour animation of base reflectivity data from the Melbourne, Florida NWS radar, showing
progress of the derecho-producing squall line over central Florida on March 12-13, 1993. "Ping-pong" animation begins
at 10:40 p.m. EST March 12 (0340 UTC March 13), and ends at 5:40 a.m. (1040 UTC) March 13. Color enhancement scale not
shown. Toward the end of the sequence, two well-defined small-scale bowing segments appear over the Atlantic coastal waters
within the larger-scale bow. Both were associated with embedded supercells. In the wake of the intense squall line,
a band of much weaker convection marks the cold front trailing southwest from the parent storm system along the mid-Atlantic
coast.

While the derecho was moving through Florida, it also was affecting Cuba.
The event caused ten deaths and many injuries in western and central Cuba. Economic losses in Cuba exceeded
one billion U.S. dollars. The squall line crossed Cuba and the adjacent coastal waters during the morning of March 13th
with two bands of very intense wind gusts (Figure 4). These were associated with smaller-scale bow echoes embedded
in the squall line. The western band extended from the western tip of Cuba along the north coast to beyond
Havana, while the eastern one reached from east of the Isle of Pines across central Cuba. Gusts to more than 100 mph
were measured in the Havana area, and a survey conducted by a research team from the Institute of Meteorology
of Cuba suggests that the maximum wind speeds may have reached 130 mph. Figure 5 provides a radar view
of the bow echo associated with the western band of intense winds as it approached Havana.

Figure
4. Measured wind gusts (mph) associated with the March 12-13,
1993 serial derecho as it crossed western and central Cuba. The
colored areas on the map indicate where wind gusts ranged
from 65 to 75 mph (green), 75-100 mph (light red) and 100 mph
or greater (dark red). (Modified from Alfonso and Naranjo 1996)

Figure
5. Radar reflectivity image (green) of the derecho-producing squall
line and associated bow echo as seen by the Havana radar at 2:59
a.m. EST March 13, 1993. The bow echo was approaching Havana,
and winds above 100 mph were occurring. The red arrow is pointed
toward an apparent embedded supercell that may have enhanced
the strength of the bow echo winds. (From Alfonso and Naranjo
1996)